On Thu, 13 Jun 2024 17:34:03 +0200 Ilya Leoshkevich <iii@xxxxxxxxxxxxx> wrote: > Architectures use assembly code to initialize ftrace_regs and call > ftrace_ops_list_func(). Therefore, from the KMSAN's point of view, > ftrace_regs is poisoned on ftrace_ops_list_func entry(). This causes > KMSAN warnings when running the ftrace testsuite. > > Fix by trusting the architecture-specific assembly code and always > unpoisoning ftrace_regs in ftrace_ops_list_func. > > The issue was not encountered on x86_64 so far only by accident: > assembly-allocated ftrace_regs was overlapping a stale partially > unpoisoned stack frame. Poisoning stack frames before returns [1] > makes the issue appear on x86_64 as well. > > [1] https://github.com/iii-i/llvm-project/commits/msan-poison-allocas-before-returning-2024-06-12/ > > Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx> > Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx> > --- Acked-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx> -- Steve > kernel/trace/ftrace.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > index 65208d3b5ed9..c35ad4362d71 100644 > --- a/kernel/trace/ftrace.c > +++ b/kernel/trace/ftrace.c > @@ -7407,6 +7407,7 @@ __ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip, > void arch_ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip, > struct ftrace_ops *op, struct ftrace_regs *fregs) > { > + kmsan_unpoison_memory(fregs, sizeof(*fregs)); > __ftrace_ops_list_func(ip, parent_ip, NULL, fregs); > } > #else
